1. Field of the Invention
The invention relates to a method and apparatus for rapid changeover of differently shaped inserts equipped with internal heating/cooling channels.
2. The Prior Art
Various direct and indirect temperature controlling systems are known for plastic injection molding, which is inherently a thermodynamic cycle process. Direct temperature control by circulating a fluid within a portion of the insert is often needed when utilizing metal inserts, as opposed to glass. Typically, these circulating channels communicate with additional channels located below or to the side of the insert. Sealing the channels is of great importance, as any fluid infiltration into the molding cavity will inhibit the production of acceptable lenses.
U.S. Pat. No. 6,290,882 shows the upper portion of fluid circulating channels 27 within the part-forming inserts in FIG. 1. These channels terminate in open-ended apertures that are presumably sealed with O-rings to corresponding apertures in the respective insert support plates, as shown in FIG. 5. Since the patent is related to thermodynamic control, there is no teaching of how the inserts are secured in place, or how an individual insert could be utilized to mold parts of different thicknesses.
U.S. Pat. No. 4,664,854 illustrates preferred electrical heating element 50 for mold 5 and water circulating heater 30 for mold 3, in FIG. 1. In order to maintain the channel in alignment, movable frame section B is clamped over a shoulder portion of mold 3. Such a configuration makes it difficult to exchange mold inserts as the equipment must cool down before disassembly. In addition, since the insert depends on a fixed distance between the parting line, the cooling channel and the locking shoulder, one insert cannot be height adjusted to mold lenses of different thicknesses.
The following three references, U.S. Pat. Nos. 5,512,221, 5,792,392 and 6,156,242 all show a single loop circulating channel which employs an O-ring on the input and output side to seal to a corresponding opening in the insert support plate.
The following two references, U.S. Pat. Nos. 5,783,233 and 5,792,492 both show a spiral loop circulating channel with one O-ring interior of the inner most loop and another O-ring exterior of the outer most loop.
Accordingly it would be desirable to provide direct thermal control while maintaining mold cleanliness and convenient insert exchange capabilities.